public class Circle {

    private static final double pai = 3.14;
    public double area(double radius) {
        return pai * radius * radius;
    }
    public static void main(String[] args) {

        Circle circle = new Circle();

        double radius = 10;

        double area = circle.area(radius);
        System.out.println("这个圆的半径是 " + radius + " 面积是 " + area);
    }
}
